The invention relates to a machine tool for the machining of a workpiece by way of a relative movement between the workpiece and a tool, comprising a machine frame, a support arranged on the machine frame and having a first receiving means for the workpiece or the tool, a cross slide system arranged on the machine frame and having a second receiving means for the tool or the workpiece. The second receiving means which can be moved by the cross slide system relative to the first receiving means in the direction of two cross slide movement axes extending transversely to one another in a movement zone of a cross slide movement surface determined by maximum paths in these cross slide movement directions.
Machine tools of this type are known from the state of the art. In these cases, the cross slide system is constructed such that it has a first slide, which can be moved only in a first cross slide movement direction and can be driven by a drive, and a second slide which is arranged on the first slide and is guided and can be driven only in the direction of a second cross slide movement direction.
With such cross slide systems, large masses are, on the one hand, to be moved so that either the speeds which can be achieved must be low or the drive power high and, on the other hand, inaccuracies in the guidance and any guidance play present are added together, which results in an impairment of the precision of the movement of the second receiving means relative to the first.
The object underlying the invention is therefore to improve a machine tool of the generic type with respect to the characteristics of the cross slide system.
This object is accomplished in accordance with the invention, in a machine tool of the type described above, in that the cross slide system comprises two slide elements. One of the slide elements is supported on the machine frame and the other slide element bears the second receiving means. The slide elements are guided so as to be movable on one another by a single two-dimensional guide means movable in the direction of both cross slide movement axes. This guide means determines the precision of the guidance of the second receiving means parallel to the cross slide movement surface. A drive device is provided, which enables the slide element bearing the second receiving means to be moved and fixed in position relative to the other slide element in the two cross slide movement directions with a defined alignment of the slide elements relative to one another.
The advantage of the inventive solution is that, as a result of providing a single two-dimensional guide means, the problems with respect to precision and play are reduced and, moreover, the masses to be moved can be reduced since it is no longer necessary to also move guide means and drive for the second moved slide on the first moved slide.
Furthermore, a sufficiently large base for the guide means of the second receiving means in relation to the machine frame and thus a large guidance rigidity can be achieved with the inventive solution in a simple manner.
A two-dimensional guide means of this type may be realized in a particularly simple manner when a first one of the slide elements has at least one guide surface extending parallel to the cross slide movement surface and when a second one of the slide elements is supported on this guide surface with at least one supporting element.
In this respect, it is particularly expedient when the guide surface has an areal (surface) extension in the direction of the cross slide movement directions which corresponds at least to the surface extension of the movement zone.
As a result of such a guide surface, which can, for example, be machined as a flat surface with the highest precision, the precision of the two-dimensional guide means can be achieved in a simple manner.
In order to ensure as stable a support as possible of the slide element bearing the second receiving means, it is preferably provided for the first slide element to have two guide surfaces arranged at a distance from one another.
With respect to the surface extension of the area of the guide surface which is acted upon with a force during the guidance of the slide element bearing the second receiving means, many embodiments are conceivable. In principle, it would be conceivable to allow the surface extension of the area acted upon with a force to vary, for example, dependent on the relative position of the slide elements in relation to one another.
However, since the precision of guidance of the slide elements could be impaired as a result, it is particularly advantageous when the surface extension of the area of the guide surface acted upon with a force is approximately the same size in all the positions of the slide elements relative to one another.
The surface extension of the area of the guide surface acted upon with a force may be kept constant in a particularly simple manner when this is predetermined by the design of the supporting element and when the surface extension of the guide surface is of such a size that in all the positions of the slide elements relative to one another the supporting element acts on the guide surface with the predetermined surface extension.
When several supporting elements are used, there is the problem of the alignment of the several supporting elements relative to one another and relative to the guide surface.
For this purpose, it is provided in one advantageous embodiment for at least one of the supporting elements to be adjustable relative to the second slide element.
A constructionally preferred solution provides for the supporting element to be designed as a supporting bar.
The guidance of the second slide element on the first slide element having the guide surface may be brought about in a variety of ways. For example, it would be conceivable to provide the second slide element with a guide surface and roller members resting thereon as supporting element so that the roller members, with which the guide surfaces are supported on one another, act between the two guide surfaces, wherein the roller members can roll along the guide surfaces in both cross slide movement directions.
In an alternative example embodiment, the at least one guide surface extending parallel to the cross slide movement surface may be designed as at least one sliding surface and the second slide element may be guided by at least one sliding support surface of the supporting element resting on the at least one sliding surface so as to be non-tiltable relative to the cross slide movement surface but displaceable therein two-dimensionally.
The advantage of this solution is that the necessity of providing roller members is dispensed with and large forces acting on the guide surface can also be absorbed in a simple manner. Moreover, the sliding guidance has the advantage of a considerable attenuation.
In order to keep the area of the sliding surface acted upon with a force the same size, in particular, in the case of a sliding surface as guide surface and a support surface acting on this sliding surface, it is preferably provided for the sliding support surface to have a smaller surface extension than the sliding surface and for the sliding support surface to rest on the sliding surface over its entire area in each position of the slide elements relative to one another.
The support surface may be held on an adjustable supporting element so that a precise adjustment of the guidance at the sliding surface is possible with this adjustable supporting element, in particular, when several support surfaces are provided.
A particularly favorable solution with respect to the support for the second receiving means provides for the supporting element to be arranged on the slide element bearing the second receiving means. This solution has the advantage that the supporting element is always arranged at a constant distance from the second receiving means in all the positions of the slide element bearing the second receiving means. Therefore the slide element bearing the second receiving means is always supported on the slide element supported on the machine frame via the supporting elements and thus the slide element is always in the same geometrical relation to the second receiving means, irrespective of the positions of the slide elements relative to one another. In contrast, for example, with the case of a cross slide system, constructed from two linear guide means, the support of the receiving means borne by the cross slide system relative to the linear guide means supported on the machine frame varies in that the second receiving means can be brought into various positions along the additional linear guide means extending transversely thereto.
This advantage of the inventive solution leads to an increase in the precision of the machining of the machine tool since the deformations which are possible due to the geometrical arrangement of the second receiving means relative to the supporting elements are independent of the position of the slide elements relative to one another.
Within the scope of the preceding explanations concerning the inventive solution, it has not been specified in more detail how the cross slide movement surface is intended to be aligned relative to the axes required for the machining of the machine tool.
In theory, it would be possible to arrange the cross slide movement surface parallel to X and Y axes of the machine tool.
One particularly favorable solution does, however, provide for the cross slide movement surface to extend parallel to a plane of movement defined by the X axis and the Z axis of the machine tool.
This solution has the advantage that inaccuracies in the guidance of the slide elements relative to one another in the cross slide movement surface have only an insignificant effect on the precision of the machining since they cause only a movement of the slide element bearing the second receiving means transversely to the plane of movement and, therefore, have no direct influence on the position in the plane of movement. As a result, the positioning in the plane of movement is defined exclusively by the drive device and, therefore, the control.
As a result, the precision of the machine tool may be determined, in particular, in the case of drive devices controlled by the machine control, essentially by the positions predeterminable by the control and the precision is not appreciably influenced in any negative way by guidance inaccuracies.
A further advantageous solution provides for guide surfaces of the slide element supported on the machine frame to be located on both sides of an opening, through which a base member of the slide element bearing the second receiving means passes. As a result, a particularly simple construction is possible, with which access to the second receiving means can be realized in a simple way from a side of the slide element bearing the second receiving means facing away from this receiving means.
A particularly favorable solution provides, for example, for a drive for the second receiving means to be located on a side, which is located opposite the second receiving means, of the base member, which passes through the opening, of the slide element bearing the second receiving means.
When the second receiving means is designed as a tool turret, such a drive may, for example, serve to drive the tool turret for carrying out indexing movements.
It is, however, also conceivable for a drive for the second receiving means to serve to drive tools arranged in the second receiving means themselves.
With respect to the design of the machine tool, it has merely been ascertained thus far that a workpiece can be arranged in one of the receiving means and a tool in the other receiving means.
In this respect, it would, for example, be conceivable for a workpiece held stationarily in the one receiving means to be machined by a rotating tool held in the other receiving means.
In this case, the receiving means is merely a so-called clamping means for the workpiece, relative to which the rotating tool is moved.
A particularly favorable solution does, however, provide for the one receiving means to be designed as a workpiece spindle and the other receiving means as a tool carrier. In this case, it is possible to carry out so-called classical lathe machinings, with which the workpiece is caused to rotate by the workpiece spindle.
The tools may be either classical stationary lathe tools or also rotatingly driven tools.
In addition, it is also possible with a workpiece spindle of this type to carry out machinings of the workpiece by turning the workpiece by means of a C axis movement controlled by a machine control.
In the case of a receiving means designed as a workpiece spindle it is particularly advantageous when the cross slide movement surface extends parallel to a spindle axis of the receiving means designed as a workpiece spindle and parallel to a direction transverse to the spindle axis.
In this case, the inaccuracies of the guidance of the slide elements relative to one another in the cross slide movement surface have an effect on the precision of the machining which is especially insignificant since they lead only to an insignificant or negligible change in the distance between workpiece and spindle axis whereas the positioning of workpiece and tool carrier relative to one another in the plane of movement can be predetermined exactly by the drive device.
In order to ensure that the supporting element always remains in contact with the guide surface and does not lift away from it, a holding down device is provided in one advantageous inventive solution and this device holds the at least one supporting element so as to abut on the at least one guide surface.
The holding down device may, in this respect, be designed in the most varied of ways. For example, it is possible to design the holding down device such that it always keeps the supporting element in contact with the guide surface with a force.
This force may be brought about, for example, by a device generating a pressure force which can be designed, for example, as a hydrostatic sliding bearing or also as a drive acting upon the supporting element in the direction of the guide surface.
A solution advantageously benefitting the guide properties of the two-dimensional guide means provides for the holding down device to have at least one additional guide surface, which extends parallel to the cross slide movement surface. The surface extension of the additional guide surface in the direction of the cross slide movement directions corresponds at least to the surface extension of the movement zone, and has an additional supporting element which acts on the guide surface.
In principle, the additional guide surface and the additional supporting element may be arranged optionally on the slide elements. It is, however, particularly advantageous from a constructional point of view when the additional guide surface is arranged on the first slide element and the additional supporting element on the second slide element.
In this respect, it is particularly favorable when the first slide element is provided with the guide surface on one side and with the additional guide surface on the opposite side.
An alternative solution provides for the guide surface and the additional guide surface to be arranged on a base member of the first slide elements so as to face one another.
In this respect, in the cases where the guide surface and the additional guide surface are arranged on the first slide element, the supporting element and the additional supporting element are preferably arranged on the second slide element.
With respect to the arrangement of the drive device relative to the slide elements and the second receiving means, no further details have so far been given.
One particularly favorable solution provides for the drive device to engage on a side of the slide element bearing the second receiving means which is located opposite the second receiving means.
As a result, it is possible to arrange the drive device such that it is located outside a working space, in which the second receiving means is arranged for the positioning of the workpiece or tool.
As a result, it is possible, in particular, in the case of a metal-cutting machining to provide the drive device outside the working space which is subjected to dirt contamination.
It is also particularly expedient when the drive device is arranged on a side of the slide element supported on the machine frame which is located opposite the second receiving means, so that the drive device is, as a result, located completely outside the working space.
Another favorable solution provides for the drive device to be arranged on a side of a machine base member located opposite the second receiving means, with the slide element supported on the machine frame being fixed on this base member, so that the entire drive device can be advantageously arranged automatically by means of the entire machine base member and the slide elements supported on it. Therefore, the provision of complicated covers for the protection of the drive device itself is superfluous and, consequently, covers are provided only for the protection of the areas over which the slide elements slide relative to one another.
With respect to the drive device for the slide element bearing the second receiving means, no further details have been given in conjunction with the preceding explanations concerning the individual embodiments. It is, however, necessary within the meaning of the inventive solution for the drive device to determine not only a definite position of the slide elements relative to one another but also a definite alignment of the slide elements relative to one another.
Particularly when it is of significance for the second receiving means to be positioned in a suitable rotary alignment in relation to the first receiving means, it is advantageous when the drive device is designed such that it always moves the slide elements in the same alignment relative to one another. In other words, the slide elements can be moved two-dimensionally relative to one another but the alignment of the slide elements relative to one another, once achieved, is maintained in all the positions during the two-dimensional movement.
This may be achieved, in principle, by a corresponding activation of the drive device during the movement of the slide element when the drive device is designed such that it allows all possible movements of the slide element.
This may be realized particularly favorably when the drive device forms an at least partial mechanical parallel guide means for the slide elements.
In principle, it would be conceivable to design the drive device as a conventional, two-dimensional drive device, i.e. with two one-dimensional drives each operative in one of the cross slide movement directions.
One particularly favorable solution does, however, provide for the drive device to engage on the slide element bearing the second receiving means at at least two points of engagement arranged at a distance from one another with three drive arms which extend in at least two different directions. The drive device can be activated by a machine control and have an articulated head. The points of engagement may be positionable in a defined manner relative to the first slide element by means of the three drive arms.
Such a solution has the great advantage that with it the masses to be moved may be reduced to a considerable degree on account of the drive device.
In this respect, it is preferably provided for each of the drive arms to be articulatedly mounted in a pivot bearing relative to the other slide element. A linear drive may be associated with each of the drive arms.
In this respect, it is possible to design the drive arms to be invariant in length and to move the pivot bearings by means of the linear drives so that the movement of each pivot bearing is transferred to the point of engagement on the slide element bearing the second receiving means by means of the drive arms of invariant length.
Alternatively thereto, one particularly favorable solution provides for the pivot bearings to be arranged so as to be stationary relative to the other slide element and for the drive arms to be designed so as to be variable in length by means of the associated linear drive.
Such a design of a drive arm variable in length may be realized in a particularly simple manner when the drive arm can be adjusted by means of a spindle drive to be variable in length.
A particularly favorable solution provides for a drive motor for the linear drive to be arranged in the region of the pivot bearing so that this drive motor need not also be moved relative to the pivot bearing but rather need only be co-rotated about the pivot bearing. In this manner, a considerable reduction in the forces of inertia which occur can be achieved.
A particularly favorable guidance of the slide element bearing the second receiving means may be achieved when two of the drive arms form a parallel guide means.
Such a formation of a parallel guide means by way of two drive arms may be achieved either with drive arms which are invariant in length in that their pivot bearings are moved parallel to one direction either by a linear movement device or by two synchronized linear movement devices.
In the case of drive arms which are variable in length, another solution provides for the two drive arms to be synchronously adjustable in length by way of the machine control.
For example, this may be achieved via a control which activates the drive motors for the length adjustment in such a manner that both drive arms always have the same length.
Additional features of the invention are the subject matter of the following detailed description as well as the drawings illustrating several embodiments.